California Asphalt Rubber Case Studies – Reduced Thickness Jack Van Kirk Basic Resources

Presentation Outline What is Asphalt Rubber Where has it been used successfully Caltrans reduced thickness design guidelines and supporting research Cost-effective strategies Advantages of asphalt rubber

Definition of Asphalt Rubber Uses a minimum of 20 +/- 2 % crumb rubber Uses 2mm size crumb rubber Reacts/interacts crumb rubber for a minimum of 45 min. at elevated temperatures Modifies original properties of asphalt cement

Crumb Rubber Modifier

Ground tire rubber is received in 2,000 pound “Supersacks”.

Current Use Asphalt Rubber Strategies Asphalt Rubber Hot Mix (ARHM) Asphalt Rubber Chip Seal Asphalt Rubber Cape Seal Multi-Layer Systems

Where have Asphalt Rubber strategies been used successfully?

Caltrans Reduced Thickness Design Guideline Caltrans developed the guidelines in 1992 Based on laboratory and long-term field data (two decades) Supported by research efforts

Design of Asphalt Rubber Pavements Uses a deflection based design method Up to 50 % reduction in thickness compared to conventional AC design thickness Over 1000 reduced thickness projects

Structural Equivalencies Thickness (mm) DGACARHM-GG ARHM-GG on a SAMI

Ravendale Project First project to use reduced thickness Asphalt Rubber pavements when compared to the conventional AC design thickness Different thickness test sections of Asphalt Rubber and conventional AC mixes were placed for comparison

75mm 45mm 45mm 45mm 75mm 45,60,75,150mm

45mm AR over SAMI 16 yrs old

75mm AR over SAMI 16 yrs old

Council On Scientific and Industrial Research (CSIR) Caltrans conducted a research project with CSIR, UCB, and Dynatest Consulting to verify the reduced thickness theory for Asphalt Rubber pavements The research used accelerated pavement testing (APT) using the heavy vehicle simulator (HVS) The research included laboratory testing to support the field testing

Original condition of pavement in South Africa

75 mm Conv. AC 38 mm ARHM 25 mm ARHM

Repetitions Wheel Load AC Overlay Section (75mm) ARHM-GG Section (38mm) ARHM-GG Section (25mm) 0-100,00040kNFine cracks at 100,000 __ 100,000 to 175,000 40kNBlock cracks at 175,000 __ Wheel load Changed to 80 kN 175,000 to 200,000 80kNCompletely cracked __ Fine cracks 200,000 to 237,000 80kNTest stopped __ Completely cracked Surface Temperature Reduced to –5 C 237,000 to 250,000 80kNTest stopped1/2 of section cracked Test stopped Performance

Supporting Research UAF (Raad) - Conducted laboratory beam fatigue testing of ARHM-GG and conventional DGAC and concluded that ARHM-GG had significant improvement in fatigue properties OSU (Hicks) and UNR (Epps) - Conducted life cycle cost analysis and concluded that Asphalt Rubber was more cost-effective when compared to conventional AC pavement maintenance and rehabilitation strategies

Asphalt Rubber 3-Layer Systems Asphalt Rubber binder used in hot mix and chip seals can be used in different thin layer systems These systems can save hundreds of thousands of dollars when compared to full reconstruction using conventional strategies

Asphalt Rubber SAMI Caltrans conducted field trials using Asphalt Rubber stress absorbing membrane interlayers (SAMI) In 1991 Caltrans concluded that SAMI’s in AC overlays of AC pavements with aggregate base are equivalent to approximately 52mm of AC in retarding initial cracking

Randolph Avenue Costa Mesa, CA

37mm ARHM-GG ARCS 25mm AC 10 years old

Philadelphia Street Whittier, CA

37mm ARHM-GG ARCS 25mm AC 10 years old

Los Angeles, CA Thin Asphalt Rubber Overlays

25mm ARHM-GG 1 year old

5 years old

10 years old

Advantages of Asphalt Rubber Binder Significantly higher binder contents - 20 % higher in dense graded mixes % higher in gap graded mixes % higher in open graded mixes Thicker film thickness Reduced oxidation Increased durability Increased resistance to reflective cracking

Advantages of Asphalt Rubber Pavement Strategies More abrasion resistant Reduced oxidation Increased fatigue resistance Can reduce thickness Reduced construction time/Increased safety Savings in energy and natural resources Lower maintenance cost

Why choose Asphalt Rubber strategies? Has a long term performance history (over 30 years) Over 1000 successful reduced thickness projects Proven alternative to costly reconstruction Established life cycle cost-effectiveness

Asphalt Rubber = Performance Thank you!